Group-mediated physical activity promotion and mobility in sedentary patients with knee osteoarthritis: results from the IMPACT-pilot trial.

OBJECTIVE: To compare the effects of a group-mediated cognitive behavioral exercise intervention (GMCB) with traditional center-based exercise therapy (TRAD) on objectively assessed levels of physical activity (PA) and mobility in sedentary patients with knee osteoarthritis (OA). METHODS: The Improving Maintenance of Physical Activity in Knee Osteoarthritis Trial-Pilot (IMPACT-P) was a 12-month, 2-arm, single-blind, randomized controlled pilot study designed to compare the effects of GMCB and TRAD on 80 sedentary patients with knee OA with self-reported difficulty in daily activities [mean age 63.5 yrs, 84% women, mean body mass index (BMI) 32.7 kg/m(2)]. Objective assessments of PA (LIFECORDER Plus Accelerometer) and mobility (400-m walk) were obtained at baseline, 3 months, and 12 months by study personnel blinded to participants' treatment assignment. RESULTS: Intent to treat 2 (treatment: GMCB and TRAD) × 2 (time: 3 mos and 12 mos) analyses of covariance of controlling for baseline, age, sex, and BMI-adjusted change in the outcomes demonstrated that the GMCB intervention yielded significantly greater increases in PA (p < 0.01) and a nonsignificant yet more favorable improvement in mobility (p = 0.09) relative to TRAD. Partial correlation analyses also revealed that change in PA was significantly correlated with the 400-m walk performance at 3-month (r = -0.51, p < 0.01) and 12-month (r = -0.40, p < 0.01) followup assessments. CONCLUSION: Findings from the IMPACT-P trial suggest that the GMCB treatment resulted in significantly greater improvement in PA and nonsignificant yet more favorable change in mobility relative to TRAD.

Weight status and differences in mobility performance, pain symptoms, and physical activity in older, knee osteoarthritis patients.

Knee osteoarthritis (OA) is a leading cause of functional disability among American adults. Obesity is a strong independent risk factor for OA. While research emphasizes the role of obesity in the OA-physical function relationship, the extent to which weight status impacts salient physical, health, and pain measures in older, knee OA patients is not well delineated. The primary aim of this study was to assess differences in mobility performance (stair climb and 400-meter walk), mobility-related self-efficacy, pain symptoms (WOMAC), and measures of accelerometer-determined physical activity (PA) as a function of weight status. Analysis of covariance was conducted to examine differences on the dependent variables. Obese class III patients were outperformed by their counterparts on nearly every measure of mobility, mobility-related self-efficacy, and the assessment of pain symptoms. These outcomes did not differ among other weight comparisons. Normal weight subjects outperformed classes I, II, and III counterparts on most measures of PA (engagement in moderate or greater PA and total weekly steps). Additionally, overweight participants outperformed obese class II participants and obese class I participants outperformed obese classes II and III participants on total weekly steps. Collectively, these findings underscore the meaningful differences observed in relevant OA outcomes as a function of increasing levels of body weight.

Effects of insulin resistance on skeletal muscle growth and exercise capacity in type 2 diabetic mouse models.

Type 2 diabetes mellitus is associated with an accelerated muscle loss during aging, decreased muscle function, and increased disability. To better understand the mechanisms causing this muscle deterioration in type 2 diabetes, we assessed muscle weight, exercise capacity, and biochemistry in db/db and TallyHo mice at prediabetic and overtly diabetic ages. Maximum running speeds and muscle weights were already reduced in prediabetic db/db mice when compared with lean controls and more severely reduced in the overtly diabetic db/db mice. In contrast to db/db mice, TallyHo muscle size dramatically increased and maximum running speed was maintained during the progression from prediabetes to overt diabetes. Analysis of mechanisms that may contribute to decreased muscle weight in db/db mice demonstrated that insulin-dependent phosphorylation of enzymes that promote protein synthesis was severely blunted in db/db muscle. In addition, prediabetic (6-wk-old) and diabetic (12-wk-old) db/db muscle exhibited an increase in a marker of proteasomal protein degradation, the level of polyubiquitinated proteins. Chronic treadmill training of db/db mice improved glucose tolerance and exercise capacity, reduced markers of protein degradation, but only mildly increased muscle weight. The differences in muscle phenotype between these models of type 2 diabetes suggest that insulin resistance and chronic hyperglycemia alone are insufficient to rapidly decrease muscle size and function and that the effects of diabetes on muscle growth and function are animal model-dependent.

Improving maintenance of physical activity in older, knee osteoarthritis patients trial-pilot (IMPACT-P): design and methods.

Promoting increased physical activity participation is now consistently advocated in the medical management of knee osteoarthritis (OA). Unfortunately, physical activity interventions targeting older knee OA patients are plagued by high attrition rates and poor long-term adherence. Consequently, identifying effective approaches for promoting maintenance of physical activity participation is integral for the successful behavioral management of knee OA. The present study, the Improving Maintenance of Physical Activity in Knee Osteoarthritis Pilot Trial (IMPACT-P), was a single-blind two-arm, randomized controlled pilot study designed to contrast the effects of a group-mediated cognitive behavioral (GMCB) exercise intervention with those of traditional center-based exercise therapy approach (TRAD) in older, knee OA patients. A total of 80 older adults with symptomatic knee OA were randomly assigned to GMCB or TRAD interventions. The primary outcome of the IMPACT-P study was changed in self-reported (CHAMPS questionnaire) and objectively assessed (LIFECORDER EX Plus) physical activity participation of moderate intensity or greater. Secondary outcomes include physical function, quality of life, and social cognitive variables. Outcomes were obtained at baseline, 3 month, and 12 month assessments by trial personnel blinded to participants' randomization assignment. Discussion. Determining the comparable efficacy of the GMCB and TRAD exercise interventions in producing meaningful improvements in physical activity and OA outcomes could enhance the efficacy of implementing physical activity participation in the behavioral management of symptomatic knee OA.